1. Field of the Invention
The present invention relates to integrated circuits and more particularly to an optical integrated circuit that uses optical elements formed of silicon nanoclusters.
2. Description of the Related Art
Photonics and optoelectronics are the terms used to describe interactions between optical and electronic physical phenomena. This can involve the changing of electrical signals into optical signals or the reverse. It can involve the modulation of electronic signals by interactions with optical signals or the reverse. Since crystalline silicon is the dominant material in microelectronics, there has been intensive research to develop silicon as an optoelectronic material. Since silicon manufacturing techniques are very mature, photonic applications could be rapidly realized if the optical interactions could be mediated in silicon structures. Under normal circumstances and conditions, silicon is an indirect band gap semiconductor, unable to emit light efficiently or fast. Optical signal processing, routing and switching is highly desirable because the speeds associated with light are much higher than those associated with electronic interactions. Moreover, photons are not affected by magnetic fields, and optical signals can cross one another without interference. These features provide great incentive to develop photonics in place or as an adjunct to electronics in many applications. Accordingly, the quest for silicon based photonic devices remain a major research activity. Existing prior art discusses only component level implementations of the silicon devices without an attempt to unify their implementations.
For example, U.S. Pat. No. 6,297,095, issued to Muralidhar et al., discloses the use of silicon nanoclusters to create a memory device with a floating gate. The patent also discusses techniques useful in the manufacturing of the device. However, there is no discussion regarding integrating this device with any other kind of optical element.
U.S. Pat. No. 6,319,427, issued to Ozin et. al., discloses the use of silicon nanoclusters capable of photoluminescence to emit fast photons. There is discussion of the means for preparing the nanoclusters. Mention is made that the specific means for manufacture of these optoelectronic devices allows them to be used in conjunction with standard silicon semiconductors. But there is no mention of their use with other nanocluster technology and there is no mention of integration of the device with other specific opto-electronic devices.
L. Pavesi et. al., Optical Gain in Silicon Nanoclusters, Nature, Vol. 408, Nov. 23, 2000, pages 440-444, have described how silicon nanoclusters can be made to emit light by a means that is both efficient and demonstrates optical gain. The key feature is the small size of the silicon nanoclusters. The structures are three nanometers in diameter. Consequently, the number of silicon atoms that are at the interface to the silicon dioxide host are comparable to those silicon atoms that interface to other silicon atoms. Any electronic states that result from the formation of the interface will behave as if they are part of the silicon band structure itself. It was found that there was an interface state that could act as the ground or terminal electronic state for emission of light from silicon. Effectively, this allows silicon to become a direct band gap emitter, greatly increasing its efficiency.
In a broad aspect, the optical integrated circuit of the present invention includes a substrate; and, a plurality of optical elements supported by the substrate being optically coupled with each other, each optical element comprising silicon nanoclusters and having a desired opto-physical interaction with light impinging thereon.
These optical elements may be, for example, optical sources, optical waveguides, optical switches and optical detectors.
The advantages with an integrated optical circuit, as it is being presented herein, are analogous to the advantages when integrated electronic circuits were first introduced. In the short term, an optical integrated circuit will be much smaller than a circuit produced by connecting components. The optical circuit can be manufactured quickly and monolithically. Since the optical elements share a common substrate, the manufacture is more robust, allowing it to survive harsher mechanical environments (i.e. the circuit can be subjected to higher acceleration and jerk without loosing mechanical integrity). The use of common physical materials implies that the circuit will undergo uniform expansion and contraction with temperature. Thus, the circuit can survive larger changes in temperature without malfunction.
In the long term, prices per element will drop as manufacturing improves, akin to the reduction of cost per transistor on an integrated electronic circuit. The density of optical elements will increase, leading to increased device function. The small sizes will eventually allow technical synthesis into technology that could benefit from optical devices, but presently cannot because of size and sensitivity.
Other objects, advantages, and novel features will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.